MRSA rates and antibiotic susceptibilities from skin and soft tissue cultures in a suburban ED

Background: Prior studies suggest that more than half of all skin and soft tissue infections (SSTIs) are caused by methicillin-resistant Staphylococcus aureus (MRSA). These data mainly represent inner-city urban centers. Objective: We determined the bacteriologic etiologies and antibiotic susceptibilities from wound cultures in the emergency department (ED). We hypothesized that in a suburban ED, MRSA would not represent the major pathogen. Methods: The study design was a retrospective, electronic medical record review in a suburban tertiary care ED with 80,000 annual visits. Subjects included ED patients of all ages who had skin or soft tissue cultures obtained in 2005-2008. Demographics and clinical data, including type of SSTI (MRSA or methicillin-sensitive S. aureus [MSSA]), culture results, and antibiotic susceptibility, were analyzed using descriptive statistics. Results: From the 1246 cultures obtained during the study period, 252 (20.2%) were MSSA and 270 (21.6%) were MRSA. The rates of MRSA infections over time increased from 13.5% to 25.7% during 2005-2008. The rates of MRSA in males and females were comparable at 23.3% and 19.6%, respectively. In 2008, MRSA was 97-100% susceptible to vancomycin, linezolid, rifampin, nitrofurantoin, chloramphenicol, gentamycin, tetracycline, and trimethoprim-sulfamethoxazole (TMP-SMZ). To a lesser extent it was susceptible to clindamycin (75%), erythromycin (62%), and levofloxacin (50%). Conclusions: There has been a significant increase in the rates of MRSA SSTIs in a suburban ED, yet only 1 in 4 SSTIs are caused by MRSA. Both MRSA and MSSA are completely susceptible to vancomycin, linezolid, rifampin, nitrofurantoin, and chloramphenicol. Gentamicin, tetracycline, and TMP-SMZ cover > 97% of both isolates.